During the long winter, he appeared increasingly sad and withdrawn.

withdrawn 是动词 withdraw 的过去分词形式，在这里作形容词使用。withdraw 由前缀 with-（表示"向后"）和 draw（"拉"）组成，本意是"撤回、收回"。 withdrawn 作形容词时，形容人"内向的、孤僻的"，就像把自己从社交中"抽离"出来一样。